Light integrators are generally used in applications where it is desired to direct light from a relatively small source to a larger field of uniform illumination. A light integrator, such as a glass or plastic light rod or a mirrored light tunnel, is commonly used for homogenizing the output of a lamp in a projection display system to provide uniform illumination to a spatial light modulator(s) (“SLM”). One type of SLM, commonly known as a digital light processor or (“DLP”), uses an array of electronic micromirrors to direct light from the light integrator to a display screen of a display system. Some display systems use a scrolling color wheel between the output of the light integrator and DLP to scroll bands of color across the DLP. The scrolling color bands are synchronized with the electronic control signals provided to the DLP to create a full-color image on the display screen. The rate of scrolling is sufficiently high that the viewer sees a full-color image, and the color scrolling is not noticeable.
Proper alignment of the light integrator to the light source and alignment of the light integrator to the color wheel and SLM is important for generating a high-quality image. The light integrator typically has a clear aperture in the input face, which is otherwise reflective. Light from the lamp is focused to enter the light integrator through the aperture, where it reflects off the walls of the light integrator and leaves the light integrator as a light beam, which is aligned to the color wheel. Such alignment has typically been done using an optical bench; however, it is desirable to align the optical components in a display system, i.e. a ready-to-use display product shipped to a consumer.
When a solid light rod is used as the light integrator, the multiple reflections off the wall generally occur according to the principle of total internal reflection (“TIR”). Touching the wall of a light rod often disrupts the TIR at the point of contact. In some instances, considerable heat can escape from the light rod and cause localized heating. Touching the wall of the light rod can also create an optical artifact that degrades the homogeneity of the light beam exiting the light rod.